Cheats after you beat the game

When you're playing a single player game press start,go to options then go to cheats. You have to unlock the cheats by getting enemy intel which are laptops that you find on different levels the levels you find them are:

Level 2 - 2 Intel Pieces
Level 4 - 2 Intel Pieces
Level 5 - 3 Intel Pieces
Level 6 - 2 Intel Pieces
Level 7 - 2 Intel Pieces
Level 9 - 3 Intel Pieces
Level 10 - 2 Intel Pieces
Level 12 - 2 Intel Pieces
Level 13 - 3 Intel Pieces
Level 14 - 2 Intel Pieces
Level 16 - 2 Intel Pieces
Level 17 - 1 Intel Piece
Level 18 - 2 Intel Pieces
Level 19 - 2 Intel Pieces

The cheats are:

Unlock CoD Noir:
Collect 2 pieces of enemy intel and ALL gameplay will turn black and white.

Unlock Photo-Negative:
Collect 4 pieces of enemy intel and ALL of the colours in the game will be inversed.

Unlock Super Contrast:
Collect 6 pieces of enemy intel and the contrast in the game will increase resulting in the dark areas becoming darker and the light areas becoming lighter.

Unlock Ragtime Warfare:
Collect 8 pieces of enemy intel and gameplay will turn black and white and dust and scratches will appear on the screen. This mode plays at 2x speed and the background music becomes piano music.

Unlock Cluster Bombs:
Collect 10 pieces of enemy intel and when one of your frag grenades explodes another four will explode in a cross-shape

Unlock A Bad Year:
Collect 15 pieces of enemy intel and when you kill enemies they will explode into old tires.

Unlock Slow-Mo Ability:
Collect 20 pieces of enemy intel and when you use the melee button you will be able to change the game to slow-mo and play at half-speed.

Unlock Infinite Ammo:
Collect 30 pieces of enemy intel and your wepaons will have unlimited ammo (does not include single-shot weapons like RPGs or C4 and Claymores).

And to unlock higher ranks you have to have xbox live.If you do then keep playing until you get enough experience (exp) points to go up a level. Every time you kill someone it brings you up a certain amount of exp.On certain maps you get extra exp for killing people.
Hope I helped: HanzUnderground

Yoo have to get intel's then you press start then go to options then press cheats then they will be automatically there just press it and for higher ranks you have to have xboxlive then you just kill and kill then you get higher ranks by points

1. Private First Class
2. Private I
3. Private II
4. Lance Corporal
5. Lance Corporal I
6. Lance Corporal II
7. Corporal
8. Corporal I
9. Corporal II
10. Sergeant
11. Sergeant I
12. Sergeant II
13. Staff Sergeant
14. Staff Sergeant I
15. Staff Sergeant II
16. Gunnery Sergeant
17. Gunnery Sergeant I
18. Gunnery Sergeant II
19. Master Sergeant
20. Master Sergeant I
21. Master Sergeant II
22. Master Gunnery Sergeant
23. Master Gunnery Sergeant I
24. Master Gunnery Sergeant II
25. 2nd Lieutenant
26. 2nd Lieutenant I
27. 2nd Lieutenant II
28. 1st Lieutenant
29. 1st Lieutenant I
30. 1st Lieutenant II
31. Captain
32. Captain I
33. Captain II
34. Major
35. Major I
36. Major II
37. Lieutenant Colonel
38. Lieutenant Colonel I
39. Lieutenant Colonel II
40. Colonel
41. Colonel I
42. Colonel II
43. Brigadier General
44. Brigadier General I
45. Brigadier General II
46. Major General
47. Major General I
48. Major General II
49. Lieutenant General
50. Lieutenant General I
51. Lieutenant General II
52. General
53. General I
54. General II
55. Commander

These are the ranks, you unlock by killing enemies online, and completing objectives online.